Data Structures & GeoDatabase

1. Data Structures & GeoDatabase GeoDatabase

2. GeoDatabase • Implemented in a relational database • Comes in two flavors – Personal & Enterprise (Access & Sys. Like Oracle) • Supports a model of topologically integrated feature classes - 2D & 3D • Supports Data Models -- ArcHydro • Use can be simple or very complex! • In some applications database designers will be needed to tune the database operation! • Can use many different data structures

3. Outline • Before looking at GeoDatabases we need to take a detailed look at the structure of the various types of data that can be used in a GeoDatabase • Then we can look at the complexities of the GeoDatabase its self

4. Data Structures ü ü ü ü ü ü ü Images ü

5. Data Structures • You have to know something about these Vector structures • Shapefiles (multiple files same name) • Coverages (Folders) • Workstation – (folder with INFO file) • PC (folder WITHOUT an INFO file) • Can only open in ArcView3.3 • Can then convert to a Shapefile

6. Data Structures • You have to know something about these structures • Raster • GRIDS • Images • MrSid • Tiff • ERDAS • Etc/

7. Vector: General • Points are defined by a single x,y coordinate pair • Lines are defined by two or more x,y coordinate pairs • Polygons are defined by lines that close to form the polygon boundaries

8. 3 Shape files for map Points, lines, polys

9. Vector: Shapefiles

10. Vector: Topology • Shapefiles are said to have NO topology • But they do (see Practical Vector GIS) • WHAT IS IT??? • Topological association:spatial relationship between features that share geometry • In Coverages (Workstation & PC): spatial relationships between connecting or adjacent features in a data layer • In GeoDatabases: a set of rules applied to feature classes that explicitly define spatial relationships that must exist between features.

11. Note: • The chapter (2) in Practical Vector GIS has a lot of good information about this subject

12. Vector: Workstation Coverages • Workstation ArcInfo coverages are a very common data structure • They are stored in a workspace • A Workspace is any folder that has • An INFO folder • And a set of coverages folders that have • A bunch of .ADF files • DON’T EVER MOVE THE CONTENTS OF A WORKSPACE EXCEPT IN ARC CATALOG!

13. Vector: Workstation Coverages Line data • Workstation ArcInfo coverages are a very common data structure • A Workspace is any folder that has • An INFO folder • And a set of coverages folders that have • A bunch of .ADF files Extent These folders are all coverages Poly or Point Attribute Table An .AAT is a Arc Attribute table TIC table

14. A Coverage: points TIC

15. A Coverage: points

16. A Coverage: Arcs

17. 2 Coverages for map Can’t have Points and Polys in same coverage because polys have a label point in each poly – confusion would abound!

18. Raster data • We have looked at this structure before • Here is ESRI’s diagram • The elevation values are average for each cell in the raster • There are a number of raster formats – ESRI’s is GRID

19. GRID STRUCTURE ESRI COURSE VIEW OF SOILS AWorkspace Explorer view

20. Image data • A raster-based representation of a scene • Cell attributes are NOT like feature data • Typically produced by an optical or electronic device, • camera or • scanning radiometer. • Examples • remotely sensed data (for example, satellite data) • scanned data, and photographs. • Stored as a raster dataset of binary or integer values that represent the intensity of reflected light, heat, sound, or any other range of values on the electromagnetic spectrum. • An image may contain one or more bands.

21. Image data .tif – tagged Image File Format .tfw – Tiff world file (location) .sid – MrSID format (LizardTech) .img – ERDAS Imagine format .jpg – Joint Photographic Experts … • A raster-based representation of a scene • Cell attributes are NOT like feature data • Typically produced by an optical or electronic device, • camera or • scanning radiometer. • Examples • remotely sensed data (for example, satellite data) • scanned data, and photographs. • Stored as a raster dataset of binary or integer values that represent the intensity of reflected light, heat, sound, or any other range of values on the electromagnetic spectrum. • An image may contain one or more bands.

22. USED FOR WHAT? • Vector data – things with discrete borders • roads, minor civil divisions • Raster data – continuous surfaces • Elevation, water table, sound levels • Images – views of real world • Photos, satellite data

23. The Geodatabase • It is a single container for many feature classes (FC) (layers, {themes} of any feature class type) • Quite often the FCs are stored in Feature Datasets (FDS) • Come in two flavors • Personal in Access databases • Enterprise in large commercial databases • Oracle, DB2, SQL Server, ArcSDE

24. Feature Classes Stand alone Feature Classes Geodatabase Feature Dataset Source View

25. } Cover Line (arc) poly Anno Table point ArcCatalog view Display view

26. You need to consider ... • What will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tables • What will be the projection & data extent used? • What rules of data modification will be required? • Do you want to maintain relationships between objects of different types? • Will you be using geometric networks? • Will you require topologically related features? • Will you store custom objects?

27. Definitions What... Do all those words mean??????????

28. What will it be used for? What kind of data will be in the GDB Themes and geometry types (point, line, poly?) Attributes -- spatial or non-spatial tables What will it be used for? What kind of data will be in the GDB Themes and geometry types (point, line, poly?) Attributes -- spatial or non-spatial tables What will be the projection used? What rules of data modification will be required? Do you want to maintain relationships between objects of different types? Will you be using geometric networks? Will you require topologically related features? Will you store custom objects? You need to consider ... • Connectivity: Constraint on the type of network features that may be connected to one another • edge-junction rules • edge-edge rules • Topology: Permissible relationships of features • within a feature class • between feature classes • between features in two different feature classes

29. You need to consider ... Associations or links between two or more objects in a GDB. Relationships can exist between 1) spatial objects (features in a feature class) 2) non-spatial objects (records in a table, or 3) spatial and non-spatial objects • What will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tables What will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tables • What will be the projection used? • What rules of data modification will be required? • Do you want to maintain relationships between objects of different types? • Will you be using geometric networks? • Will you require topologically related features? • Will you store custom objects?

30. You need to consider ... • What will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tables. What will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tables • What will be the projection used? • What rules of data modification will be required? • Do you want to maintain relationships between objects of different types? • Will you be using geometric networks? • Will you require topologically related features? • Will you store custom objects? Objects: The representation of a real world entity stored in a GDB. An object has properties and behaviors.

31. You need to consider ... A one dimensional nonplaner graph (mathematics) that is composed of features.These features are constrained to exist within the network and can, therefor, be considered network features. • What will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tablesWhat will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tables • What will be the projection used? • What rules of data modification will be required? • Do you want to maintain relationships between objects of different types? • Will you be using geometric networks? • Will you require topologically related features? • Will you store custom objects?

32. You need to consider ... Relationships between connected features in a geometric network ORShared borders between features in a topology (Now that is circular!!!!) • What will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tablesWhat will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tables • What will be the projection used? • What rules of data modification will be required? • Do you want to maintain relationships between objects of different types? • Will you be using geometric networks? • Will you require topologically related features? • Will you store custom objects?

33. You need to consider ... • What will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tablesWhat will it be used for? • What kind of data will be in the GDB • Themes and geometry types (point, line, poly?) • Attributes -- spatial or non-spatial tables • What will be the projection used? • What rulesof data modification will be required? • Do you want to maintain relationships between objects of different types? • Will you be using geometric networks? • Will you require topologically related features? • Will you store custom objects? Custom Objects: In ArcGIS you are NOT limited to the objects provided. New objects can be added

34. More Definitions: Feature • An object class in a GDB that has a field of type GEOMETRY. • Are stored in Feature Classes • A representation of a real world object • A point, line or poly in a coverage or shapefile • A representation of a real world object in a layer on a map.

35. More yet: Feature Class • Conceptual representation of a category of geographic features. • Includes point, line, poly & annotation • In a GDB, an object that stores features and has a geometry field type

36. Feature Dataset • A collection of feature classes that share the same spatial reference. • It is because they share the same spatial reference that they can participate in topological relationships with each other. • Several feature classes with the same geometry may be stored in the same feature dataset. • Object geometry and relationship classes can also be stored in a feature dataset

37. Some others • Edge: • A line segment in a topology that defines lines or polys boundaries • Multiple features in one or more feature classes may share topology edges • Dataset: • Any feature class, table, or collection of feature classes or tables in the GDB • A named collection of logically related data items arranged in a prescribed manor

38. Icons GDB Feature Dataset GDB table

39. Icons GDB Feature Dataset GDB table

40. Icons GDB Feature Dataset GDB table

43. GDB Three ways to create a GDB Plan it Create a Schema with ArcCatalog Import Existing Data Topic for FOR558! Use CASE tools Define connectivity rules, relationships Load data into Schema:ShapefilesCoverages

44. Feature Datasets (FDS) • Exist in a GDB to define a particular Spatial Reference • Are a way to group feature Classes(FC) with the same spatial reference • So they can participate in topological relationships with each other • Topologically related FCs must reside in the same FDS

45. Spatial Reference • A coordinate System • Geographic • UTM • Etc. • A spatial domain (coord range, measures (M), and Z values (extent) • Precision (# of system units/unit M) • MUST be specified when creating a FDS and it feature classes or a stand alone feature class

46. Field Properties • When creating a Feature Class or table you can specify the number of fields to be included • And you can spec settings such as field type and max. size • All fields have property default values, domains, aliases, and null allowance

47. Field Properties • When creating a Feature Class or table you can specify the number of fields to be included • And you can spec settings such as field type and max. size • All fields have property default values, domains, aliases, and null allowance Valid set or range of values for the field Set values at creation time Yes or NO for allowing nulls (nothing) Aliases will display on maps

48. Field Precision & Scale • Max. field size and precision • Precision – number of digits (not the “.”) • Scale – number of decimal places • Personal GDBs support ONLY binary fields and precision and scale are ignored! • NOT SO for enterprise GDB!!!

49. Required Fields • Apply to all feature classes and tables • Automatically created • Required fields also have required properties (domain) [can’t change] • Required fields for simple FCs are • OBJECTID • Shape • Note: when you import data there will be other fields you cannot change in ArcGIS – But you can change them in ACCESS

50. Topologies • Many datasets have features that could share boundaries or corners • By creating a Topology you set up rules defining how features share their geometries. • Editing a boundary or vertex shared by two or more features updates the shape of all of them.